For years, our field and industry have been bandying around rule-of-thumb statistics, chief among them that somewhere between 25-50% of people 65 and over have hearing loss that is sufficient to interfere with normal communication.  Who knows where that statistic came from? It’s a heuristic that’s gained the mantel of truth over time.  And the stated range of 25 to 50%, was too broad to be of much use except by a few practitioners who brandished it to scare people into buying hearing aids.

Such was the situation in 2011 when Dr Frank Lin and colleagues at Johns Hopkins summarized the situation in a seminal paper on prevalence of hearing loss in US Seniors:

“Hearing loss has been associated with cognitive and functional decline in older adults and may be amenable to rehabilitative interventions, but national estimates of hearing loss prevalence and hearing aid use in older adults are unavailable.” (Lin et al. 2011)

 

Johns Hopkins Starts an Avalanche

 

A plethora of studies with real, verifiable statistics began to emerge in 2011 as part of national epidemiological studies of health and aging.  Lin et al (2011) set off the avalanche by accessing and analyzing National Health and Nutritional Examination Survey (NHANES) data, which measured hearing for the first time in 2005/6, when 717 seniors were scrutinized in terms of their audiometric thresholds and hearing histories (e.g., noise exposure, hearing aid use). 

Taken together with other study data on subjects’ medical histories and demographics, our field received its first report out from the Lin Research Group at Johns Hopkins group on the true prevalence of hearing loss and hearing aid use in different groups of seniors (see Table 1).  The research was especially important to hearing practitioners and their patients because the statistics were “generalizable to the U.S.population.” 

Findings were also of special importance to our field and to consumers because the researchers distinguished hearing decreases from hearing loss. Hearing can decrease without creating enough “loss” to create communication problems, so it makes sense to only call it a hearing loss/impairment if it causes communication difficulty.  Lin et al (2011) categorized their subjects according to the World Health Organization’s  (WHO) definition that people have a hearing impairment only when their hearing thresholds drop to the  point that it “…affects their ability to hear human speech.”  When thresholds hit that point, it is a “mild” hearing loss; greater drops produce “moderate” or greater hearing loss.

Table 1.  Hearing Loss (defined in terms of hearing impairment) and Hearing Aid Use in US senior populations.

Hearing Loss in People in the US Aged 70 and Up

Hearing Aid Use by Degree of Hearing Loss in People Aged 70 and Up

63% (white)

40% (black)

Moderate Hearing Loss

Mild Hearing Loss

40.0%

3.4%

There are lots of rich data in this and subsequent studies.  As expected, men have more hearing loss than women. Other findings are shown in Table 1.  Perhaps because the cut-off age for seniors is 70 instead of the traditional 65, the results show more hearing loss in seniors than that old “25-50%” range indicated.  Unexpected was the finding that hearing loss is more common in older whites than in blacks.  It will be interesting to find out as further research is done whether this reflects a “protective” genetic pattern or is due to environment exposure differences between the two groups.

 

Laments 

 

The 2011 Lin et al study found low treatment rates for seniors with hearing loss sufficient to cause problems with speech understanding.  Fewer than half of seniors with moderate hearing loss wore hearing aids.  Only 3.4% of those with mild hearing loss did.  This is lamentable but not unexpected.

 “…only a minority of older people with these impairments use hearing aids …There’s a general perception that hearing loss in older adults is not very important.”  (FR Lin, NYTimes)

Here’s another lament.  The connection between uncorrected hearing loss and mental health appears strong and devastating.  Those who cannot maintain good communication due to hearing loss tend to withdraw, lose social connections, experience depression, and have poorer health than those who “treat” their hearing loss and maintain good communication via hearing aids.

Here’s a further lament. There are strong neuroscientific arguments for age effects on auditory and cognitive processing, though not for the scare tactics we’re seeing in some current hearing aid advertising. In the long run, as research is compiled linking hearing aid use to daily function, it’s not unlikely that the the “use it or lose it” mantra of the gym will have applications to auditory and cognitive functions as well. In the meantime, as research delves into these areas, those who address their hearing losses with amplification when their hearing losses are mild may be nipping impairment in the bud and maintaining functionality.

 

Paths of Actions for Consumers and Providers 

 

Laments aside, there are things that can be done now.  There is ongoing research to guide present-day decision-making.  Smart patients with a strong drive to maintain communication and connectivity are likely to do something about perceived hearing problems. What they do is likely to be guided by their access to data and study conclusion.  To the extent that these assumptions hold up, audiologists are encouraged to think of active seniors as people who are:

  • getting more empowered to handle their hearing difficulties,
  • accessing research to gain informed opinions on what actions are in their best interests, and 
  • communicating their viewpoint by their actions as well as their words-of mouth to their friends, associates, and hearing healthcare providers.

In support of those views, next week’s post provides a lengthy compilation of salient research from 2011 to the present, accompanied by the investigators’ conclusions.

 

References

 

Lin FR, Thorpe R, Gordon-Salant S, Ferrucci L. Hearing loss prevalence and risk factors among older adults in the United States. The Journals of Gerontology Series A: Biological Sciences and Medical Sciences. 2011;66(5):582-590. 

 Nieman CL et al.  The Baltimore HEARS Pilot Study: An Affordable, Accessible, Community-Delivered Hearing Care Intervention. Gerontologist. 2016 Dec 7. pii: gnw153. [Epub ahead of print]

Pichora-Fuller, K & Singh G. Effects of Age on Auditory and Cognitive Processing: Implications for Hearing Aid Fitting and Audiologic Rehabilitation. Trends Amplif. 2006 Mar; 10(1): 29–59. doi:  10.1177/108471380601000103

Rabin, R.C.  Aging: Hearing Loss Is Common but Often Ignored. New York Times (March 10, 2011). 

In recent years, research from animal models and now human modeling has suggested a brain locus for tinnitus, rather than the ear-level origin assumed previously.  

 Research into tinnitus has become much more sophisticated of late, and is changing the common understanding of the disorder and providing the first testable model of human tinnitus that could provide some new avenues for therapy. (AAAS Eureka Alert)

 

Tinnitus, a Common but Confusing Condition

 

Tinnitus is an odd affliction of the auditory system, not unlike the “phantom pain” that afflicts many who have lost a limb.  People with tinnitus perceive sounds that they variously describe as ringing, buzzing, humming, cicada-like, etc.  But, their perception doesn’t match reality:  the sounds they hear are phantom sounds heard only by them.  The phantom sounds, like phantom pain, are a side effect of bodily damage.  In the case of tinnitus, the ringing/buzzing is an early warning sign that the person has sustained damage to hair cells in the inner ear.  Damaged inner ear hair cells eventually cause hearing loss.

Tinnitus is the most common disorder of the auditory system, affecting upward of 40 million people in the US. The diagnosis of tinnitus is based solely on the patient report, since the physician or audiologist cannot hear the tinnitus, measure it directly, or visualize inner ear hair cells.  Until recently, research into tinnitus has been limited by these factors.   The surge in tinnitus research is driven, in part, by new imaging techniques. But the high incidence of tinnitus complaints in returning veterans with hearing loss caused by exposure to loud explosions is also spurring researchers in other fields such as neurophysiology to look at tinnitus. 

 

The Georgetown University LINC

 

Brain imaging studies in humans with tinnitus have been underway for some years at the Laboratory of Integrative Neuroscience and Cognition (LINC) at Georgetown University Medical Center (GUMC).  The reason brain imaging is so important to tinnitus is because those studies are pointing to hyperactivity in the brain’s central auditory system as the primary source of tinnitus.  

The researchers suggest that tinnitus works like this:  it starts when hair cells are damaged, which sends a message to the brain’s central auditory pathways that there is a problem; the brain centers reorganize to respond to the damage.  Here’s a paraphrase/quote from the researchers:

Receptors in the auditory parts of the brain aren’t receiving perceive sensory input from the damaged hair cells anymore, so they compensate by firing spontaneously and frequently, which produces the initial tinnitus signals.  The brain fills in sensations in response to a deficit of input. Neighboring frequencies become amplified and expand into the vacated frequency range. It also happens to people with a hole in their retina. They don’t see the hole because the brain fills in what is missing. 

 

Old Brain Structures and Network Dysfunctions

 

This is really interesting stuff, but here’s where it gets REALLY interesting.  In normal auditory brain regions, the researchers have discovered a feedback system that cancels out the unreal sounds of tinnitus by a process known as “inhibition.”  The feedback system is regulated down in the “old brain” in an area called the limbic system, which precedes awareness/consciousness. 

The limbic system is central to emotional regulation and there is some suggestion that people who suffer from tinnitus are also more likely to suffer from chronic pain, depression, insomnia, and jaw clenching (Roberts et al., 2010).  Georgetown LINC studies by Leaver et al (2011 & 2016) found that tinnitus-related neural hyperactivity was even greatest in limbic structures, especially in the nucleus accumbens , which is involved in cognitive processing and implicated in addictive behaviors. Morever, the hyperactivity was specific to sounds which were matched in frequency to the patients’ own tinnitus.  

We definitely know that tinnitus affects people’s quality of life (QOL).  As one of the Georgetown LINC researchers comments:

people with tinnitus may “have an independent, systemic vulnerability in one or more neurotransmitter systems in the limbic region. That could explain why drugs that modulate neurotransmitters like serotonin appear to help some people out….It appears tinnitus is the auditory symptom of an underlying syndrome, which becomes evident in patients who happen to have a hearing loss.” (J.P. Rauschecker,PhD)

 

Developing Tinnitus Treatments

 

Future research is aimed at identifying neurotransmitters that are involved in the brain’s noise cancellation system. If those can be identified, the thought is that they might be used as a therapeutic drug therapy to treat tinnitus in such a way that patients’ noise cancellation systems are restored.  Quoting Dr. Rauschecker once more:   

“If we can find a way to turn that feedback system back on to eliminate phantom sound, it might be possible one day to take a pill and make tinnitus go away.”

 

References 

 

 Imaging reveals how brain fails to tune out phantom sounds of tinnitus.  Press Release from Georgetown University Medical Center.

Leaver, A. et al. (Jan 13, 2011). Dysregulation of limbic and auditory networks in tinnitus.  Neuron, 69(1), pp 33-43.

Roberts, LE et al. (Nov 10 2010).  Ringing Ears: The Neuroscience of Tinnitus. J Neuroscience, 30(45), pp 14972-14979.

 

Feature image from emedicinehealth